(1) Field of the Invention
The present invention relates to a precision optical fiber winding device and more particularly to a winding machine which permits precise control of reel drag, traversing speed, mandrel rotation speed, fiber tension and fiber lay angle.
(2) Description of the Prior Art
Certain interferometric optical hydrophones are based upon the phenomena that an optical fiber, when elongated, will alter the characteristics of the light transmitted in proportion thereto. A compliant, cylindrical mandrel such as a nylon rod or the like, when circumferentially wrapped with optical fiber, can take advantage of this phenomenon. This wrapped elastomeric mandrel, when exposed to an acoustic pressure, changes its length and, due to Poisson Effects, diameter. The optical fiber, being prestretched by tightly wrapping it around the mandrel, follows these diameter changes and thus elongates or contracts the optical path length in proportion to the acoustic signal. By way of example, a more complete description of a typical fiber optic hydrophone is set forth in U.S. Pat. No. 4,238,856.
At present interferometric hydrophones have mandrels handwrapped with the delicate optical fiber. A significant drawback of the handwrapped hydrophone is the lack of repeatable performance between one hydrophone and the next. This is because once mandrel material has been chosen, hydrophone performance depends strongly on two constructional parameters. First, the amount of initial fiber elongation present after the winding process dictates how easily the fiber will continue to elongate as the mandrel diameter increases or shrinks with diameter reduction. This fiber prestretch is directly controlled by the amount of back tension applied as the fiber is wound onto the mandrel. Handwrapping the fiber does not allow sufficient tension control during this initial fiber elongation. The second constructional parameter governing hydrophone performance is the distribution pattern of the fiber along the length of the mandrel. This fiber density is entirely dependent upon the lay angle of the fiber as it is wound onto the mandrel. Handwrapping does not permit the angular control necessary for consistent performance from hydrophone to hydrophone.